Trailering assist system for vehicle

ABSTRACT

A method of assisting a driver in maneuvering a vehicle with a trailer hitched to the vehicle includes equipping a vehicle with a trailering assist system that includes (i) a camera disposed at the vehicle and viewing a trailer that is hitched the vehicle and (ii) a control having an image processor. During a reversing maneuver of the vehicle and trailer, image data is captured by the camera and vehicle parameters are provided to the control. Responsive to the vehicle parameters and processing of captured image data, the trailering assist system estimates an estimated trailer angle and an estimated vehicle steering wheel angle. The estimated vehicle steering wheel angle and an actual steering wheel angle are compared to determine a steering wheel angle error. The estimated trailer angle is modified in subsequent determinations of the estimated trailer angle based at least in part on the determined steering wheel angle error.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/316,939, filed Jun. 27, 2014, now U.S. Pat. No. 10,755,110,which claims the filing benefits of U.S. provisional application Ser.No. 61/840,542, filed Jun. 28, 2013, which is hereby incorporated hereinby reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to rear vision systems forvehicles and, more particularly, to rear vision systems having arearward facing camera at a rear portion of a vehicle.

BACKGROUND OF THE INVENTION

Rear backup cameras and vision systems are known for use in vehicles.Examples of such systems are described in U.S. Pat. Nos. 7,859,565;6,611,202; 6,222,447; 5,949,331; 5,670,935 and/or U.S. Pat. No.5,550,677, which are hereby incorporated herein by reference in theirentireties. Such systems may display images for viewing by the driver ofthe vehicle that provide a view rearward of the vehicle.

SUMMARY OF THE INVENTION

The present invention provides a trailer angle prediction system ortrailering assist system for a vehicle that includes at least one cameradisposed at a vehicle and having an exterior field of view rearward ofthe vehicle. The camera is operable to capture image data. A controlincludes an image processor operable to process captured image data. Thecontrol of the trailering assist system is operable, such as in responseto image processing and/or one or more trailer/vehicle parameters, todetermine a trailer angle of a trailer that is towed by the vehicle, andthe control of the trailering assist system may be operable to determinea path of the trailer responsive to a steering angle of the vehicle. Thecontrol of the trailering assist system may predict the steering wheelangle of the vehicle (based on the determined trailer angle and othertrailer/vehicle parameters) and compare that with the measured ordetermined or actual steering wheel angle to determine an error oroffset. The trailering assist system may correct for the offset toenhance the trailer angle determination and/or to enhance reversing ofthe vehicle and trailer along a selected or appropriate rearward path.The trailering assist system may be operable to display information forviewing by the driver to assist the driver in driving the vehicle withthe trailer, and may display the predicted path that the trailer andvehicle are traveling along and/or the appropriate path to reverse thetrailer to a selected location or parking area.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a vehicle equipped with the rear vision systemand trailer detection system of the present invention, shown towing atrailer;

FIG. 2 is schematic of the vehicle and trailer of FIG. 1;

FIG. 3 is a block diagram of the prediction states of the trailer angledetection system of the present invention; and

FIG. 4 is a block diagram of the trailer angle detection system of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and the illustrative embodiments depictedtherein, a vehicle 10 includes an imaging system or vision system 12that includes one or more imaging sensors or cameras (such as a rearwardfacing imaging sensor or camera 14 a and/or a forwardly facing camera 14b at the front (or at the windshield) of the vehicle, and/or asidewardly/rearwardly facing camera 14 c, 14 d at the sides of thevehicle), which capture images exterior of the vehicle, with the camerashaving a lens for focusing images at or onto an imaging array or imagingplane of the camera (FIG. 1). The vision system 12 is operable toprocess image data captured by the cameras and may provide displayedimages at a display device 16 for viewing by the driver of the vehicle.In the illustrated embodiment, the vehicle is towing a trailer 18 andthe vision system 12 may include one or more cameras (or receives andprocesses image data captured by one or more cameras at the trailer),such as a rearward facing camera 20 a at the rear of the trailer andsidewardly facing cameras 20 b, 20 c at the sides of the trailer. Thesystem, responsive to processing of image data captured by the cameras14 a-d (and optionally cameras 20 a-c), may be operable to display abird's eye view or top down view of the vehicle and trailer to assiststhe driver in maneuvering the vehicle with the trailer, such as during areversing maneuver of the vehicle and trailer. Optionally, the visionsystem or trailering assist system may process image data to detectobjects, such as objects to the rear of the subject or equipped vehicleduring a reversing maneuver, or such as approaching or followingvehicles or vehicles at a side lane adjacent to the subject or equippedvehicle or the like.

The trailer angle viewing system or trailering assist system of thepresent invention may utilize aspects of the trailer angle detectionsystems described in International Publication No. WO 2012/103193,and/or U.S. patent applications, Ser. No. 14/102,981, filed Dec. 11,2013, now U.S. Pat. No. 9,558,409, and/or Ser. No. 14/036,723, filedSep. 25, 2013, now U.S. Pat. No. 9,446,713, which are herebyincorporated herein by reference in their entireties.

As discussed in U.S. patent applications, Ser. No. 14/102,981, filedDec. 11, 2013, now U.S. Pat. No. 9,558,409, and/or Ser. No. 14/036,723,filed Sep. 25, 2013, now U.S. Pat. No. 9,446,713, which are herebyincorporated herein by reference in their entireties, the display systemmay provide a projection of the trailer's position during a reversingmaneuver. The normal view of a backup camera on a trailer pullingvehicle is typically blocked by the trailer, and thus such a backupcamera cannot provide visual backup assistance to the driver when thetrailer is attached to the vehicle. However, the camera system of thepresent invention may be operable to detect the angle of the trailerlongitudinal axis with respect to the pulling vehicle's longitudinalaxis, and with the knowledge of the trailer dimensional characteristics(such as wheel position and distance from the vehicle and the like), theprocessor can calculate and project a trajectory or reversing path ofthe trailer in the form of graphic overlay on the camera display orvideo display (typically disposed in the vehicle, such as at or in ornear an interior rearview mirror assembly of the vehicle) to indicate tothe driver viewing the video display a path or trajectory of where thetrailer is backing up to during the vehicle and trailer reversingmaneuver. In addition, when the trailer pulling or towing vehicle isequipped with side view cameras, the added views provided by the sidecameras (typically having fields of view directed generally rearwardlyand sidewardly with respect to the direction of forward travel of theequipped vehicle) can provide additional scene information of thetrailer to assist the driver of the vehicle (viewing the images at avideo display of the vehicle) during a reversing or backing up maneuver.The calculated graphical trailer path can be overlaid to the side cameraimage to further assist the driver of the vehicle during a reversing orbacking up maneuver.

Most drivers find it challenging to back up a trailer on their vehicledue to the dynamic interaction between the relative positions of thevehicle, trailer and front vehicle wheel angles. Most drivers use atrial and error method where they attempt to learn the results of thevarious stages of the maneuver by making short trial runs. The presentinvention provides a determination of the trailer angle (the angle ofthe longitudinal axis of the towed trailer relative to the longitudinalaxis of the towing vehicle) and a prediction or estimation of thetrailer angle, such as based on the vehicle dynamics and the vehicle andtrailer parameters. The trailer angle detection and prediction system ortrailering assist system is useful in assisting a driver in parking atrailer at a parking space.

As shown in FIG. 2, various parameters of the vehicle and the trailerthat is being towed by the vehicle can be measured or determined and/orinput into the system of the present invention. The system of thepresent invention is operable to determine the trailer angle or predictthe trailer angle when the vehicle is stopped and/or moving in a forwarddirection and/or moving in a rearward direction. The system maydetermine or estimate some of the parameters (such as the length ordistance (L1) between the vehicle rear axle and he hitch point, thelength or distance (L2) between the hitch point and the trailer axle andtrailer angle relative to the vehicle), with less dependence on userinputs. For example, the system may estimate or predict some of theparameters while the vehicle is traveling forward, and may predict theinitial trailer angle before reversing. The trailer angle prediction maybe continuously updated while the trailer is reversing, whereby thetrailer angle estimation may be used for self-parking of thevehicle-trailer combination.

As shown in FIG. 4, the system may use some of the vehicle and/ortrailer parameters (such as trailer length, vehicle length, vehiclewidth and distance between the rear axle of the vehicle and the trailerhitch point or point where trailer pivots relative to the towingvehicle) as inputs and, based on the inputs, the system may estimate thetrailer angle (such as via a trailer angle estimator) and the vehiclewheel angle (such as via a wheel angle estimator), which is thencompared to the input value or vehicle wheel angle to determine an errorbetween the actual wheel angle (such as determined by a steering wheelangle or wheel angle sensor) and the estimated wheel angle. Theestimation process of the trailer angle detection or prediction systemor trailering assist system of the present invention thus uses thevehicle inputs and parameters to estimate the trailer angle relative tothe towing vehicle, and estimates the trailer angle for the givendriving condition and steering direction or steering angle.

For example, during a reversing maneuver of the vehicle, the system maydetermine an estimated trailer angle and, using the estimated trailerangle, may estimate the steering angle or wheel angle of the towingvehicle (based on the vehicle and trailer parameters and direction oftravel and/or other inputs). The estimated wheel angle of the towingvehicle is compared to the determined or measured wheel angle (such asdetermined by or received from a vehicle status system or sensor andvehicle network bus or the like). The error or difference between theestimated wheel angle and the determined or actual wheel angle is usedto modify the estimated trailer angle in subsequent determinations. Whenthe error is within a threshold level, the system may continue tomonitor the angles as the driver of the vehicle continues the drivingmaneuver. When the determined error is at or above a threshold level oramount, the system may alert the driver of the vehicle (such as via avisual or audible alert or the like) that the trailer angle may not beat an expected angle for that steering angle, so that the driver cancheck to make sure that the driving maneuver is guiding (pushing orpulling) the trailer in the right direction towards the targetedlocation. Optionally, during a reversing maneuver where the systemdisplays a graphic overlay to represent the trailer in the displayedimages, the system may utilize the wheel angle error determination toadjust the graphic overlay angle relative to the rear of the vehicle.The system may determine the error between estimated and actual wheelangles during both forward and rearward driving maneuvers.

The estimated trailer angle, along with the vehicle parameters, is usedto estimate the wheel angle of the vehicle for that estimated trailerangle (and that particular direction of travel of the vehicle andtrailer). The difference between the actual or determined wheel angle(such as measured or determined by a sensor or the like of the vehicle)and the estimated wheel angle is the error or offset that needs to beminimized by the driver and the system. The output of the PID controlleris used as a feedback to update the parameters used to compute thetrailer angle estimate.

The camera or sensor may comprise any suitable camera or sensor.Optionally, the camera may comprise a “smart camera” that includes theimaging sensor array and associated circuitry and image processingcircuitry and electrical connectors and the like as part of a cameramodule, such as by utilizing aspects of the vision systems described inInternational Publication Nos. WO 2013/081984 and/or WO 2013/081985,which are hereby incorporated herein by reference in their entireties.

The system includes an image processor operable to process image datacaptured by the camera or cameras, such as for detecting objects orother vehicles or pedestrians or the like in the field of view of one ormore of the cameras. For example, the image processor may comprise anEYEQ2 or EYEQ3 image processing chip available from Mobileye VisionTechnologies Ltd. of Jerusalem, Israel, and may include object detectionsoftware (such as the types described in U.S. Pat. Nos. 7,855,755;7,720,580 and/or U.S. Pat. No. 7,038,577, which are hereby incorporatedherein by reference in their entireties), and may analyze image data todetect vehicles and/or other objects. Responsive to such imageprocessing, and when an object or other vehicle is detected, the systemmay generate an alert to the driver of the vehicle and/or may generatean overlay at the displayed image to highlight or enhance display of thedetected object or vehicle, in order to enhance the driver's awarenessof the detected object or vehicle or hazardous condition during adriving maneuver of the equipped vehicle.

The vehicle may include any type of sensor or sensors, such as imagingsensors or radar sensors or lidar sensors or ladar sensors or ultrasonicsensors or the like. The imaging sensor or camera may capture image datafor image processing and may comprise any suitable camera or sensingdevice, such as, for example, a two dimensional array of a plurality ofphotosensor elements arranged in at least 640 columns and 480 rows (atleast a 640×480 imaging array, such as a megapixel imaging array or thelike), with a respective lens focusing images onto respective portionsof the array. The photosensor array may comprise a plurality ofphotosensor elements arranged in a photosensor array having rows andcolumns. Preferably, the imaging array has at least 300,000 photosensorelements or pixels, more preferably at least 500,000 photosensorelements or pixels and more preferably at least 1 million photosensorelements or pixels. The imaging array may capture color image data, suchas via spectral filtering at the array, such as via an RGB (red, greenand blue) filter or via a red/red complement filter or such as via anRCC (red, clear, clear) filter or the like. The logic and controlcircuit of the imaging sensor may function in any known manner, and theimage processing and algorithmic processing may comprise any suitablemeans for processing the images and/or image data.

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No. 61/844,630, filed Jul. 10,2013; Ser. No. 61/844,173, filed Jul. 9, 2013; Ser. No. 61/844,171,filed Jul. 9, 2013; Ser. No. 61/842,644, filed Jul. 3, 2013; Ser. No.61/840,542, filed Jun. 28, 2013; Ser. No. 61/838,619, filed Jun. 24,2013; Ser. No. 61/838,621, filed Jun. 24, 2013; Ser. No. 61/837,955,filed Jun. 21, 2013; Ser. No. 61/836,900, filed Jun. 19, 2013; Ser. No.61/836,380, filed Jun. 18, 2013; Ser. No. 61/833,080, filed Jun. 10,2013; Ser. No. 61/830,375, filed Jun. 3, 2013 and/or Ser. No.61/830,377, filed Jun. 3, 2013; which are all hereby incorporated hereinby reference in their entireties. The system may communicate with othercommunication systems via any suitable means, such as by utilizingaspects of the systems described in International Publication Nos. WO2010/144900; WO 2013/043661 and/or WO 2013/081985, and/or U.S. patentapplication Ser. No. 13/202,005, filed Aug. 17, 2011, now U.S. Pat. No.9,126,525, which are hereby incorporated herein by reference in theirentireties.

The imaging device and control and image processor and any associatedillumination source, if applicable, may comprise any suitablecomponents, and may utilize aspects of the cameras and vision systemsdescribed in U.S. Pat. Nos. 5,550,677; 5,877,897; 6,498,620; 5,670,935;5,796,094; 6,396,397; 6,806,452; 6,690,268; 7,005,974; 7,937,667;7,123,168; 7,004,606; 6,946,978; 7,038,577; 6,353,392; 6,320,176;6,313,454 and/or 6,824,281, and/or International Publication Nos. WO2010/099416; WO 2011/028686 and/or WO 2013/016409, and/or U.S. Pat.Publication No. US 2010-0020170, and/or U.S. patent application Ser. No.13/534,657, filed Jun. 27, 2012, and published Jan. 3, 2013 as U.S.Publication No. US-2013-0002873, which are all hereby incorporatedherein by reference in their entireties. The camera or cameras maycomprise any suitable cameras or imaging sensors or camera modules, andmay utilize aspects of the cameras or sensors described in U.S.Publication No. US-2009-0244361 and/or U.S. patent application Ser. No.13/260,400, filed Sep. 26, 2011, now U.S. Pat. No. 8,542,451, and/orU.S. Pat. No. 7,965,336 and/or U.S. Pat. No. 7,480,149, which are herebyincorporated herein by reference in their entireties. The imaging arraysensor may comprise any suitable sensor, and may utilize various imagingsensors or imaging array sensors or cameras or the like, such as a CMOSimaging array sensor, a CCD sensor or other sensors or the like, such asthe types described in U.S. Pat. Nos. 5,550,677; 5,670,935; 5,760,962;5,715,093; 5,877,897; 6,922,292; 6,757,109; 6,717,610; 6,590,719;6,201,642; 6,498,620; 5,796,094; 6,097,023; 6,320,176; 6,559,435;6,831,261; 6,806,452; 6,396,397; 6,822,563; 6,946,978; 7,339,149;7,038,577; 7,004,606; 7,720,580 and/or 7,965,336, and/or InternationalPublication Nos. WO 2009/036176 and/or WO 2009/046268, which are allhereby incorporated herein by reference in their entireties.

The camera module and circuit chip or board and imaging sensor may beimplemented and operated in connection with various vehicularvision-based systems, and/or may be operable utilizing the principles ofsuch other vehicular systems, such as a vehicle headlamp control system,such as the type disclosed in U.S. Pat. Nos. 5,796,094; 6,097,023;6,320,176; 6,559,435; 6,831,261; 7,004,606; 7,339,149 and/or U.S. Pat.No. 7,526,103, which are all hereby incorporated herein by reference intheir entireties, a rain sensor, such as the types disclosed in commonlyassigned U.S. Pat. Nos. 6,353,392; 6,313,454; 6,320,176 and/or U.S. Pat.No. 7,480,149, which are hereby incorporated herein by reference intheir entireties, a vehicle vision system, such as a forwardly,sidewardly or rearwardly directed vehicle vision system utilizingprinciples disclosed in U.S. Pat. Nos. 5,550,677; 5,670,935; 5,760,962;5,877,897; 5,949,331; 6,222,447; 6,302,545; 6,396,397; 6,498,620;6,523,964; 6,611,202; 6,201,642; 6,690,268; 6,717,610; 6,757,109;6,802,617; 6,806,452; 6,822,563; 6,891,563; 6,946,978 and/or 7,859,565,which are all hereby incorporated herein by reference in theirentireties, a trailer hitching aid or tow check system, such as the typedisclosed in U.S. Pat. No. 7,005,974, which is hereby incorporatedherein by reference in its entirety, a reverse or sideward imagingsystem, such as for a lane change assistance system or lane departurewarning system or for a blind spot or object detection system, such asimaging or detection systems of the types disclosed in U.S. Pat. Nos.7,881,496; 7,720,580; 7,038,577; 5,929,786 and/or U.S. Pat. No.5,786,772, and/or U.S. provisional applications, Ser. No. 60/628,709,filed Nov. 17, 2004; Ser. No. 60/614,644, filed Sep. 30, 2004; Ser. No.60/618,686, filed Oct. 14, 2004; Ser. No. 60/638,687, filed Dec. 23,2004, which are hereby incorporated herein by reference in theirentireties, a video device for internal cabin surveillance and/or videotelephone function, such as disclosed in U.S. Pat. Nos. 5,760,962;5,877,897; 6,690,268 and/or U.S. Pat. No. 7,370,983, and/or U.S.Publication No. US-2006-0050018, which are hereby incorporated herein byreference in their entireties, a traffic sign recognition system, asystem for determining a distance to a leading or trailing vehicle orobject, such as a system utilizing the principles disclosed in U.S. Pat.No. 6,396,397 and/or U.S. Pat. No. 7,123,168, which are herebyincorporated herein by reference in their entireties, and/or the like.

Optionally, the circuit board or chip may include circuitry for theimaging array sensor and or other electronic accessories or features,such as by utilizing compass-on-a-chip or EC driver-on-a-chip technologyand aspects such as described in U.S. Pat. No. 7,255,451 and/or U.S.Pat. No. 7,480,149 and/or U.S. Publication No. US-2006-0061008 and/orU.S. patent application Ser. No. 12/578,732, filed Oct. 14, 2009, nowU.S. Pat. No. 9,487,144, which are hereby incorporated herein byreference in their entireties.

Optionally, the vision system may include a display for displayingimages captured by one or more of the imaging sensors for viewing by thedriver of the vehicle while the driver is normally operating thevehicle. Optionally, for example, the vision system may include a videodisplay device disposed at or in the interior rearview mirror assemblyof the vehicle, such as by utilizing aspects of the video mirror displaysystems described in U.S. Pat. No. 6,690,268 and/or U.S. patentapplication Ser. No. 13/333,337, filed Dec. 21, 2011, now U.S. Pat. No.9,264,672, which are hereby incorporated herein by reference in theirentireties. The video mirror display may comprise any suitable devicesand systems and optionally may utilize aspects of the compass displaysystems described in U.S. Pat. Nos. 7,370,983; 7,329,013; 7,308,341;7,289,037; 7,249,860; 7,004,593; 4,546,551; 5,699,044; 4,953,305;5,576,687; 5,632,092; 5,677,851; 5,708,410; 5,737,226; 5,802,727;5,878,370; 6,087,953; 6,173,508; 6,222,460; 6,513,252 and/or 6,642,851,and/or European patent application, published Oct. 11, 2000 underPublication No. EP 0 1043566, and/or U.S. Publication No.US-2006-0061008, which are all hereby incorporated herein by referencein their entireties. Optionally, the video mirror display screen ordevice may be operable to display images captured by a rearward viewingcamera of the vehicle during a reversing maneuver of the vehicle (suchas responsive to the vehicle gear actuator being placed in a reversegear position or the like) to assist the driver in backing up thevehicle, and optionally may be operable to display the compass headingor directional heading character or icon when the vehicle is notundertaking a reversing maneuver, such as when the vehicle is beingdriven in a forward direction along a road (such as by utilizing aspectsof the display system described in International Publication No. WO2012/051500, which is hereby incorporated herein by reference in itsentirety).

Optionally, the vision system (utilizing the forward facing camera and arearward facing camera and other cameras disposed at the vehicle withexterior fields of view) may be part of or may provide a display of atop-down view or birds-eye view system of the vehicle or a surround viewat the vehicle, such as by utilizing aspects of the vision systemsdescribed in International Publication Nos. WO 2010/099416; WO2011/028686; WO 2012/075250; WO 2013/019795; WO 2012/075250; WO2012/145822; WO 2013/081985; WO 2013/086249 and/or WO 2013/109869,and/or U.S. patent application Ser. No. 13/333,337, filed Dec. 21, 2011,now U.S. Pat. No. 9,264,672, which are hereby incorporated herein byreference in their entireties.

Optionally, a video mirror display may be disposed rearward of andbehind the reflective element assembly and may comprise a display suchas the types disclosed in U.S. Pat. Nos. 5,530,240; 6,329,925;7,855,755; 7,626,749; 7,581,859; 7,446,650; 7,370,983; 7,338,177;7,274,501; 7,255,451; 7,195,381; 7,184,190; 5,668,663; 5,724,187 and/orU.S. Pat. No. 6,690,268, and/or in U.S. Publication Nos. US-2006-0061008and/or US-2006-0050018, which are all hereby incorporated herein byreference in their entireties. The display is viewable through thereflective element when the display is activated to display information.The display element may be any type of display element, such as a vacuumfluorescent (VF) display element, a light emitting diode (LED) displayelement, such as an organic light emitting diode (OLED) or an inorganiclight emitting diode, an electroluminescent (EL) display element, aliquid crystal display (LCD) element, a video screen display element orbacklit thin film transistor (TFT) display element or the like, and maybe operable to display various information (as discrete characters,icons or the like, or in a multi-pixel manner) to the driver of thevehicle, such as passenger side inflatable restraint (PSIR) information,tire pressure status, and/or the like. The mirror assembly and/ordisplay may utilize aspects described in U.S. Pat. Nos. 7,184,190;7,255,451; 7,446,924 and/or U.S. Pat. No. 7,338,177, which are allhereby incorporated herein by reference in their entireties. Thethicknesses and materials of the coatings on the substrates of thereflective element may be selected to provide a desired color or tint tothe mirror reflective element, such as a blue colored reflector, such asis known in the art and such as described in U.S. Pat. Nos. 5,910,854;6,420,036 and/or U.S. Pat. No. 7,274,501, which are hereby incorporatedherein by reference in their entireties.

Optionally, the display or displays and any associated user inputs maybe associated with various accessories or systems, such as, for example,a tire pressure monitoring system or a passenger air bag status or agarage door opening system or a telematics system or any other accessoryor system of the mirror assembly or of the vehicle or of an accessorymodule or console of the vehicle, such as an accessory module or consoleof the types described in U.S. Pat. Nos. 7,289,037; 6,877,888;6,824,281; 6,690,268; 6,672,744; 6,386,742 and/or U.S. Pat. No.6,124,886, and/or U.S. Publication No. US-2006-0050018, which are herebyincorporated herein by reference in their entireties.

Changes and modifications in the specifically described embodiments maybe carried out without departing from the principles of the presentinvention, which is intended to be limited only by the scope of theappended claims as interpreted according to the principles of patentlaw.

The invention claimed is:
 1. A method of assisting a driver inmaneuvering a vehicle with a trailer hitched to the vehicle, the methodcomprising: equipping a vehicle with a trailering assist system, thetrailering assist system comprising (i) a camera disposed at theequipped vehicle and viewing rearward so as to view a trailer that ishitched to the equipped vehicle and (ii) a control comprising an imageprocessor operable to process image data captured by the camera;capturing image data via the camera during a reversing maneuver of theequipped vehicle and trailer; providing vehicle parameters to thecontrol; responsive to the vehicle parameters provided to the controland responsive to processing of captured image data by the imageprocessor at the control, estimating via the trailering assist system anestimated trailer angle and an estimated steering wheel angle of theequipped vehicle, wherein the estimated trailer angle comprises anestimation of an angle of a longitudinal axis of the trailer relative toa longitudinal axis of the equipped vehicle; comparing the estimatedvehicle steering wheel angle to an actual steering wheel angle of theequipped vehicle to determine a steering wheel angle error; andmodifying the estimated trailer angle in subsequent determinations ofthe estimated trailer angle based at least in part on the determinedsteering wheel angle error.
 2. The method of claim 1, wherein the cameracomprises a two dimensional array of photo sensing elements.
 3. Themethod of claim 1, wherein the steering wheel angle error is derivedfrom the difference between the estimated steering wheel angle and theactual steering wheel angle.
 4. The method of claim 1, wherein, whilethe determined steering wheel angle error is within a threshold range,the trailering assist system continues to determine steering wheel angleerrors in making subsequent determinations of the estimated trailerangle as the driver of the equipped vehicle continues the reversingmaneuver of the equipped vehicle and trailer.
 5. The method of claim 1,further comprising generating an output responsive to the steering wheelangle error being at or above a threshold level.
 6. The method of claim5, wherein generating the output comprises generating an alert to thedriver of the equipped vehicle when the steering wheel angle error is ator above the threshold level.
 7. The method of claim 6, wherein thealert comprises at least one of an audible alert and a visual alert. 8.The method of claim 1, wherein the equipped vehicle comprises a videodisplay screen for viewing by the driver of the equipped vehicle, andwherein the method comprises displaying at the video display screenimages of the scene rearward of the equipped vehicle to assist thedriver during the reversing maneuver of the equipped vehicle andtrailer.
 9. The method of claim 8, comprising displaying at the videodisplay screen a graphic overlay representative of the trailer to assistthe driver during the reversing maneuver of the equipped vehicle andtrailer.
 10. The method of claim 9, further comprising generating analert to the driver of the equipped vehicle when the steering wheelangle error is at or above a threshold level to assist the driver inadjusting the actual steering angle of the equipped vehicle to guide thetrailer towards a target location.
 11. The method of claim 9, comprisingdisplaying at the video display screen information for viewing by thedriver of the equipped vehicle to assist the driver in maneuvering theequipped vehicle and trailer.
 12. The method of claim 11, comprisingdisplaying at the video display screen a predicted path that theequipped vehicle and trailer are traveling along responsive at least inpart to the estimated trailer angle.
 13. The method of claim 12,comprising displaying at the video display screen an appropriate pathfor the equipped vehicle and trailer to follow to reverse the trailertowards a target location.
 14. The method of claim 1, wherein thevehicle parameters provided to the control comprise at least twoselected from the group consisting of (i) speed of the equipped vehicle,(ii) measured steering wheel angle of the equipped vehicle, (iii)trailer length of the trailer hitched to the equipped vehicle, (iv)vehicle length of the equipped vehicle, (v) vehicle width of theequipped vehicle and (vi) trailer hitch point from a rear axle of theequipped vehicle.
 15. The method of claim 1, comprising generating viathe control an alert signal to alert the driver of a potentiallyhazardous situation during the reversing maneuver of the equippedvehicle and trailer.
 16. A method of assisting a driver in maneuvering avehicle with a trailer hitched to the vehicle, the method comprising:equipping a vehicle with a trailering assist system, the traileringassist system comprising (i) a camera disposed at the equipped vehicleand viewing rearward so as to view a trailer that is hitched to theequipped vehicle and (ii) a control comprising an image processoroperable to process image data captured by the camera; capturing imagedata via the camera during a reversing maneuver of the equipped vehicleand trailer; providing vehicle parameters to the control; responsive tothe vehicle parameters provided to the control and responsive toprocessing of captured image data by the image processor at the control,estimating via the trailering assist system an estimated trailer angleand an estimated steering wheel angle of the equipped vehicle, whereinthe estimated trailer angle comprises an estimation of an angle of alongitudinal axis of the trailer relative to a longitudinal axis of theequipped vehicle; comparing the estimated vehicle steering wheel angleto an actual steering wheel angle of the equipped vehicle to determine asteering wheel angle error, wherein the steering wheel angle error isderived from the difference between the estimated steering wheel angleand the actual steering wheel angle; modifying the estimated trailerangle in subsequent determinations of the estimated trailer angle basedat least in part on the determined steering wheel angle error; andgenerating an alert to the driver of the equipped vehicle responsive tothe steering wheel angle error being at or above a threshold level. 17.The method of claim 16, wherein, while the determined steering wheelangle error is within a threshold range, the trailering assist systemcontinues to determine steering wheel angle errors in making subsequentdeterminations of the estimated trailer angle as the driver of theequipped vehicle continues the reversing maneuver of the equippedvehicle and trailer.
 18. The method of claim 16, wherein the alertcomprises at least one of an audible alert and a visual alert.
 19. Themethod of claim 16, wherein the equipped vehicle comprises a videodisplay screen for viewing by the driver of the equipped vehicle, andwherein the method comprises displaying at the video display screenimages of the scene rearward of the equipped vehicle to assist thedriver during the reversing maneuver of the equipped vehicle andtrailer.
 20. The method of claim 16, wherein the vehicle parametersprovided to the control comprise at least two selected from the groupconsisting of (i) speed of the equipped vehicle, (ii) measured steeringwheel angle of the equipped vehicle, (iii) trailer length of the trailerhitched to the equipped vehicle, (iv) vehicle length of the equippedvehicle, (v) vehicle width of the equipped vehicle and (vi) trailerhitch point from a rear axle of the equipped vehicle.
 21. A method ofassisting a driver in maneuvering a vehicle with a trailer hitched tothe vehicle, the method comprising: equipping a vehicle with atrailering assist system, the trailering assist system comprising (i) acamera disposed at the equipped vehicle and viewing rearward so as toview a trailer that is hitched to the equipped vehicle, (ii) a controlcomprising an image processor operable to process image data captured bythe camera and (iii) a video display screen for displaying video imagesfor viewing by the driver of the equipped vehicle; capturing image datavia the camera during a reversing maneuver of the equipped vehicle andtrailer; providing vehicle parameters to the control; responsive to thevehicle parameters provided to the control and responsive to processingof captured image data by the image processor at the control, estimatingvia the trailering assist system an estimated trailer angle and anestimated steering wheel angle of the equipped vehicle, wherein theestimated trailer angle comprises an estimation of an angle of alongitudinal axis of the trailer relative to a longitudinal axis of theequipped vehicle; comparing the estimated vehicle steering wheel angleto an actual steering wheel angle of the equipped vehicle to determine asteering wheel angle error, wherein the steering wheel angle error isderived from the difference between the estimated steering wheel angleand the actual steering wheel angle; modifying the estimated trailerangle in subsequent determinations of the estimated trailer angle basedat least in part on the determined steering wheel angle error;displaying at the video display screen video images of the scenerearward of the equipped vehicle to assist the driver during thereversing maneuver of the equipped vehicle and trailer, the displayedvideo images derived from image data captured by the camera; anddisplaying at the video display screen a graphic overlay at the videoimages to assist the driver during the reversing maneuver of theequipped vehicle and trailer.
 22. The method of claim 21, wherein, whilethe determined steering wheel angle error is within a threshold range,the trailering assist system continues to determine steering wheel angleerrors in making subsequent determinations of the estimated trailerangle as the driver of the equipped vehicle continues the reversingmaneuver of the equipped vehicle and trailer.
 23. The method of claim21, further comprising generating an alert to the driver of the equippedvehicle when the steering wheel angle error is at or above a thresholdlevel to assist the driver in adjusting the actual steering angle of theequipped vehicle to guide the trailer towards a target location.
 24. Themethod of claim 21, wherein displaying the graphic overlay comprisesdisplaying at the video display screen a predicted path that theequipped vehicle and trailer are traveling along responsive at least inpart to the estimated trailer angle.
 25. The method of claim 21, whereinthe vehicle parameters provided to the control comprise at least twoselected from the group consisting of (i) speed of the equipped vehicle,(ii) measured steering wheel angle of the equipped vehicle, (iii)trailer length of the trailer hitched to the equipped vehicle, (iv)vehicle length of the equipped vehicle, (v) vehicle width of theequipped vehicle and (vi) trailer hitch point from a rear axle of theequipped vehicle.